The present invention relates to a single meter blending fuel dispensing system. More particularly, the present invention relates to a single meter blending fuel dispensing system utilizing a pair of proportional flow control valves with corresponding pressure sensors or flow meters to create an exact blend of high and low octane fuel.
It is now commonplace for fuel dispensing systems to blend different octane grade fuels into an intermediate grade for consumption. Previously, a fuel dispenser was connected to as many underground tanks as grades of fuel offered from a given dispenser. That is, there was a one to one correspondence between the octanes offered and the number of underground tanks. Each nozzle simply drew from a tank of a particular octane rating. This required expensive installation and maintenance of several underground tanks.
Currently, however, gas stations can provide many grades of fuel from only two underground tanks, a high and a low octane tank, by blending the fuels of each into the desired intermediate grade. This proves much more economical and efficient due to the reduction in the number of underground tanks.
Fuel blending is a well-known concept as evidenced by the representative prior art patent references cited below. The techniques and mechanisms used to achieve fuel blending, however, are quite variable.
U.S. Pat. No. 4,404,984 issued to Jones entitled xe2x80x9cGas-Liquid Mixing Metering Systemxe2x80x9d describes a blender which differentially senses liquid pressure and gas pressure and provides adjustment means for a valve in order to increase or decrease pressure based on current requirements.
U.S. Pat. No. 5,139,045 issued to Ensign entitled xe2x80x9cSystem for Dispensing a Fuel Mixturexe2x80x9d describes a system for blending two different fuel grades to produce a third intermediate fuel grade.
U.S. Pat. No. 5,125,533 issued to Gayer et al. entitled xe2x80x9cVariable Blending Dispensexe2x80x9d describes a variable valve system using flow-meters to calibrate and correct errors in a fuel blending system.
U.S. Pat. No. 3,999,959 issued to Bajek entitled xe2x80x9cMotor Fuel Blending Control Systemxe2x80x9d describes a system for mixing two gasoline streams having dissimilar octane ratings.
The present invention is advantageously distinguishable from each of the above references in the mechanisms and methods it uses to achieve fuel blending.
The preferred embodiment of the present invention comprises a single meter blending fuel dispensing system utilizing a pair of proportional flow control valves each having a pressure transducer positioned aft of the valve flow control mechanism. A computer controller is used to program a desired fuel mixture by varying the pressure for each flow control valve. A pressure decrease or increase in either of the valves is detected by the controller which will make adjustments to the valve flow control mechanisms in order to maintain the desired blend ratio. A third pressure transducer can be situated downstream of the valves and is set such that the pressure it receives cannot exceed that of the two valve pressures.
A second embodiment of the present invention substitutes flow meters for the pressure sensors in order to determine the amount of fuel being dispensed by the different flow paths.
The system of the present invention also provides a means for calibrating the positive displacement meter. The positive displacement meter is the highly accurate meter required to ensure that a customer receives the exact amount of fuel he is paying for. Government regulations require periodic, typically annual, testing of each fuel dispenser""s positive displacement meter since it is subject to mechanical wear. At installation, however, the positive displacement meter is at its most accurate. It is synchronized with the less accurate pressure sensors or flow meters and the data is stored. As time passes and the positive displacement meter wears, the wear can be compensated for by software using the baseline data and the pressure sensors or flow meters which are not subject to mechanical wear.
It is therefore an object of the present invention to provide a fuel blending system utilizing proportional flow control valves and corresponding pressure sensors for obtaining a desired fuel blend from the fuel blending system.
It is another object of the present invention to provide a fuel blending system utilizing proportional flow control valves and corresponding flow meters for obtaining a desired fuel blend from the fuel blending system.
It is a still further object of the present invention to provide a system and method for calibrating the highly accurate positive displacement meter within a fuel dispensing system.
Some of the objects of the invention having been stated hereinabove, other objects will become evident as the description proceeds, when taken in connection with the accompanying drawings as best described hereinbelow.